1. Field of the Invention
This invention relates to a planar antenna, more particularly to an ultra wide bandwidth planar antenna.
2. Description of the Related Art
FIG. 1 illustrates a conventional planar antenna 1 that operates within the ultra wide bandwidth, i.e., between 3.1 GHz and 10.6 GHz. The conventional planar antenna 3 includes a radiating element 10, a feeding element 11, and a grounding element 20. The radiating element 10 is generally elliptical, and has major and minor axes (a, b) that are respectively 11.21 millimeters and 10.125 millimeters in length. The grounding element 20 is generally rectangular in shape, and has a pair of long sides (c), each of which has a length of 30 millimeters, and a pair of short sides (d), each of which has a length of 10 millimeters.
The aforementioned conventional planar antenna 1 is disadvantageous in that, since each long side (c) of the grounding element 20 is longer than the minor axis (b) of the radiating element 10, the size of the conventional planar antenna 1 is relatively large. Furthermore, as illustrated in FIGS. 2 and 3, when operated from 9 GHz to 11 GHz, the conventional planar antenna 1 has radiation patterns that are not omni-directional.